Sanitizers and disinfectants are formulations intended to reduce or destroy pathogenic bacteria, fungi and viruses. Quaternary ammonium compounds serve as the active antimicrobial agent in a wide variety of these formulations currently used in the household, industrial and institutional markets. They are effective at low concentrations and provide a broad spectrum of bactericidal activity, against both gram positive and gram negative bacteria. In addition to the antimicrobial agent, the formulations usually contain co-surfactants to assist in solubilizing soil particulates, as well as chelating agents to overcome deficiencies associated with hard water, and builders or acids to aid in cleaning performance. Over the years, these formulations have been optimized to afford excellent disinfection and sanitizing efficacy as well as providing good cleaning performance. As labor costs have been increasing substantially, there has been a trend toward the one-step disinfectant/cleaners. Modern formulations both clean and disinfect or sanitize in one application. This concept has also become attractive for the household market as well, where reducing cleaning time is desirable.
Unfortunately, standard quaternaries of choice, being cationic surfactants, are quite irritating to ocular tissue. This is especially so of dialkyl quaternary ammonium chlorides which are very efficient as a disinfectant. With increased concerns over pathogens in the household environment, the need for safe disinfectants and sanitizers has increased. Therefore, there is heightened interest in safe and mild household disinfectants and sanitizers and it is desirable to obtain a disinfectant formulation that is less irritating but still efficient as a disinfectant.
The co-surfactants used in most formulations also contribute to the overall irritation profile. The commonly used co-surfactants can be classified into two categories: nonyl phenol ethoxylates (NPE) and linear alcohol ethoxylates. Unfortunately, NPE's, especially those with the best detergency, exhibit high Draize eye scores and are appropriately labelled severely to moderately irritating. Linear alcohol ethoxylates are themselves less irritating, but do little to mitigate the irritation of the quaternary.
Several methods have been employed in the prior art to address the issue of reduced ocular irritation for disinfectant and sanitizer formulations. Unfortunately, none have combined a cost effective way to reduce irritation and enhance the overall cleaning performance of the formulation. Many co-surfactants, while lessening the irritation of the quaternary, impact negatively on the biocidal efficacy of the quaternary. While it is well known that anionic surfactants cannot be used in the presence of cationics, other surfactants including ethoxylates can dramatically reduce the biocidal efficacy of quaternaries (Futura, Taro, "Effect of Alkaline Builders and Surfactants on the Bactericidal Activity of Didecyldimethylammonium Chloride", J. Antibac. Antifung. Agents (1992) 20:12, pp. 617-22 (Japanese)).
An early patent, U.S. Pat. No. 3,402,242, assigned to Parachlor Chemical, describes the use of borax (sodium tetraborate) as an additive to a quaternary formulation being applied as a spray or in nebulized form. The borax was described as reducing the irritation to eyes, nose and throat of nebulized sprays in hospital rooms, nursing homes, etc. However, in a concentrate form, the borax would not be effective in reducing the irritation of the quaternary and would leave a residue upon application.
Today most of the use of quaternary disinfectants and sanitizers is in the area of dilutable concentrates, where a small amount of concentrate is diluted with water and then used to disinfect walls, floors, furniture, etc. or in the product category called RTU, or ready-to-use. RTU products contain the quaternary at use concentration and are a widely used type of disinfectant for the household market.
It has been recognized that at use dilution concentrations, e.g., 30-100 ppm, the irritability of quaternary ammonium compounds can be reduced by the addition of amphoteric surfactants and certain nonionic surfactants at 1:1 and 10:1 surfactant/quaternary ratios. "Disinfectants and Sanitizers--Global Issues 1992" presented by L. Hall, M. Chiang and D. Dutton of Lonza Inc. at CSMA/AOCS Detergent Industry Conference, Sep. 13, 1992. However, satisfactory techniques have not been found to mitigate the irritation of formulations having a high concentration of quaternary, particularly above the critical micelle concentration (CMC).
Two patents assigned to American Cyanamid address reducing the irritation of household disinfectants. In the first, U.S. Pat. No. 4,336,151, the invention describes the use of ethoxylated cocodiethanolamide, ethoxylated lanolin, hydrolyzed animal protein, allantoin, dextrose sugar and/or imidazole to mitigate the irritation of quaternaries. While the first two agents are effective at reducing ocular irritation, both are ethoxylates based on ethylene oxide, which have been shown to contain residual traces of 1,4-dioxane, a known carcinogen. Additionally, the protein, allantoin, dextrose sugar and imidazole, while all being effective at reducing ocular irritation of quaternary-based formulations, offer no other performance benefits. Indeed, residual sugar, for instance, unless totally and completely rinsed, leads to sticky residues, attracting ants and providing a food supply for microorganisms. Thus, while the formulations described do offer reduced ocular irritation, it does not come without drawbacks.
In U.S. Pat. No. 4,336,152, the use of maltodextrin as an irritation reducing compound for d-limonene containing disinfectants is described. The use of maltodextrin reduced the irritation profile from a Draize score of 74 to 2, a very substantial change in irritation potential. However, maltodextrin, like dextrose cited in U.S. Pat. No. 4,336,151, provides nothing in the way of cleaning enhancement or lower cost and can contribute to residue or other deposits.
In none of the aforementioned patents have all the critical objectives (i.e., low cost, enhanced cleaning performance, no post-application cleanup) been achieved. Therefore, there is a long standing need to provide a cost-effective, quaternary-based formulation that is both low in ocular irritation, while providing excellent in-use cleaning and detergency. Additionally, the formulation should provide one-step cleaning and disinfection and not require post-treatment rinsing nor cleanup in order to keep labor costs contained. Finally, it would be advantageous if the formulation could be based on readily available raw materials commonly used in detergent and cleaner manufacturing.